Ask for Next Actions, person responsible and timelines, if nobody else does

Do these two things and you will either not be asked to participate (very efficient) or the meetings will become more focused just because somebody is making them to answer hard questions. And with Next Actions clarified, there may be less need for the meetings in general.

Of course, if you are no longer invited to the meetings, you need another way to know whether there was something important there. So:

Pre-meeting, schedule one-on-one with another person you trust who will go there

Post-meeting, do a postmortem/follow-up with the same person

It may seem less efficient then actually being on the meeting, but it is often better as it allows you to schedule one-on-ones better (e.g. as lunch/coffee break) and often allows (forces) you to think through your contribution/needs more.

I try to do as much as possible over email. Obviously I do have to meet and discuss things from time to time. To help those along I start with the meeting duration. Don't set an hour meeting to have a 20 minute discussion just because an hour is the default. Whatever time you set will probably get filled. If you keep to the minimum needed you have a better chance of filling that time with actual content.

Another tool that can help is to have an agenda and let people know what that is up front. This also helps keep the meeting focused on the task at hand. Also noting what the point of the meeting is. If no one knows why they are there, the meeting will probably deteriorate into a waste of time. And on that note, make sure you have the right people in the meeting.

Finally, (and one I rarely do) keep and distribute meeting notes when you do have the meeting. That won't help for the meeting you are currently in, but if people can depend on getting the information they need from reading the minutes, you will have less people cluttering up the meeting who only want to be there to make sure they don't miss anything, but have nothing to contribute, because the more people you have in a room, the more likely the meeting is to get sidetracked and be a waste of time.

I try and insist I get to chair meetings in those environments that I know are poor at managing meetings efficiently. Much of the time existing chairs are delighted to pass the role to me, as in environments where it doesn't run well, they all hate the role.

Another method I occasionally use, which is possibly counterintuitive, is to hold meetings in a coffee shop (where content is not confidential, obviously) - and ideally the ones with no seating, just the little standing tables. That way there is no inducement to get comfortable and an artificial stop point at which coffees are finished or too cold, which makes an easy get-out moment.

Assign all items on the agenda an ideal time to finish in.
Start a timer when the meeting start to time the meeting.
Start a timer at the start of each topic for half the topic time.
When the timer rings evaluate the current topic:

We are are still on topic.

We are moving towards a solution.

Now restart the timer.
If the timer rings move on to the next topic.
When the meeting time is done the meeting is over.
Unaddressed issues will stand over to a new meeting that will be organised later and every body is free to go as soon as the timer goes.

People quickly adjusts and most people are supportive of this type of meetings. This helps people feel free to tell the boss the meeting is over.

Everybody has some issues about which they are passionate and need a call from reality to make them focus on time.

Adding to Alex's point about distributing minutes after the meeting, you could mention that in the meeting's invite (that minutes will be distributed, or something to that effect) so people will know before hand and feel less inclined to attend